Soil nutrient availability affects tundra plant community composition and plant–vole interactions

Figures & data

Figure 1. Nutrient addition gradient study with simulated herbivory experimental design in three blocks, each containing four 5 × 20 m fertilization plots (CT, F2, F5, and F10). Each fertilization plot has two no-herbivory (NH), two pulse (PU), and two press (PR) individual tussocks.

Figure 2. Mean (n = 3) relative cover of growth forms/species among years (2008–2021) and fertilization treatments (see Figure 1 for nutrient levels). Relative cover was not measured in 2009, and F2 treatments were not sampled in 2010 and 2011.

Table 1. Mean (n = 3; ± SD) species richness and Shannon diversity index per 1 m² by fertilization level (see Figure 1 for treatment abbreviations) for the years 2008 and 2021. Superscript letters indicate means were significantly different within year.

	CT	F2	F5	F10
Richness
2008	12 ± 1	13 ± 2	12 ± 2	12 ± 2
2021	12 ± 1^a	11 ± 2^a	8 ± 1^b	5 ± 1^b
Diversity
2008	2.24 ± 0.10	2.23 ± 0.18	2.13 ± 0.20	2.05 ± 0.22
2021	1.98 ± 0.13^a	1.76 ± 0.08^a	1.18 ± 0.24^b	0.63 ± 0.21^b

Figure 3. Correlation between deciduous shrub and Eriophorum relative cover in each fertilization treatment. Each point represents the average for one block (n = 8 quadrats within block) for 3 points per treatment per year (2008–2021). Confidence interval around regression line is SE.

Figure 4. Mean (± SD, n = 3 except in F2 n = 2) Eriophorum tiller heights (cm) among simulated herbivory and fertilization treatments (see Figure 1 for treatment abbreviations) over four growing seasons (2018–2021). Note that tiller heights were only measured once in 2020 due to COVID-19 restrictions.

Figure 5. Final tiller heights (n = 3 except n = 2 in F2) among simulated herbivory and fertilization treatments for four growing seasons (2018–2021; treatment abbreviations in Figure 1). Xs indicate means; letters indicate significant differences among the means caused by a significant interaction between herbivory and fertilization in 2021.

Data availability statement

The data that support the findings of this study are openly available in the Arctic Long-Term Ecological Research Data Catalog at https://arc-lter.ecosystems.mbl.edu/arctic-data-catalog.